..Rather than discussing the many interesting findings and methods in this special issue, I will comment on two cross-cutting issues - one about genes and the other about the environment - that came to mind as I read these articles. ..

Common DNA markers can account for more than half of the genetic influence on cognitive abilities

..66 of the estimated heritability, reaffirming that cognitive abilities are heritable. Larger sample sizes alone will be sufficient to identify many of the genetic variants that influence cognitive abilities...

..Research that focuses on quantitative traits - including the low and high ends of normal distributions - could have far-reaching implications for the diagnosis, treatment and prevention of the problematic extremes of these traits...

..This finding held even when we excluded those children with language impairment whose nonverbal score indicated general cognitive delay. These results point to a general genetic factor that includes both language and nonverbal problems...

..The identification of specific nonshared environments responsible for the variance in behaviour problems is a key challenge...

A genome-wide association study of social and non-social autistic-like traits in the general population using pooled DNA, 500 K SNP microarrays and both community and diagnosed autism replication samples

..01 at age 11. These findings suggest that expression of FTO may become stronger throughout childhood. Increases in heritability may also be due to children increasingly selecting environments correlated with their genetic propensities...

Genetic and environmental influence on language impairment in 4-year-old same-sex and opposite-sex twins

Added value measures in education show genetic as well as environmental influence

Claire M A HaworthSocial, Genetic and Developmental Psychiatry Centre, King s College London, London, United KingdomPLoS ONE 6:e16006. 2011

..The pervasiveness of genetic influence in how and how much children learn is compatible with an active view of learning in which children create their own educational experiences in part on the basis of their genetic propensities...

More than just IQ: school achievement is predicted by self-perceived abilities--but for genetic rather than environmental reasons

Heritability of antisocial behaviour at 9: do callous-unemotional traits matter?

Essi VidingDepartment of Psychology, University College London, and SGDP Centre, Institute of Psychiatry, King s College London, London, UKDev Sci 11:17-22. 2008

..The heritability difference was even more pronounced in magnitude when hyperactive symptoms were controlled. CU traits thus appear to index one valid way of sub-typing children with early-onset AB...

Birthweight-discordance and differences in early parenting relate to monozygotic twin differences in behaviour problems and academic achievement at age 7

..Genetic overlap was significant but moderate across all raters. These findings are discussed in relation to population screening for autism and future genetic research...

Genetics of callous-unemotional behavior in children

Essi VidingKing s College London, Medical Research Council Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, De Crespigny Park, London, United KingdomPLoS ONE 8:e65789. 2013

..This GCTA ceiling is very low for CU in our study, despite its high twin study heritability estimate. The gap between GCTA and twin study heritabilities will make it challenging to identify genes responsible for the heritability of CU. ..

From learning to read to reading to learn: substantial and stable genetic influence

..There was also evidence for age-specific genetic influences at each age. Genetic influences on reading are substantial and stable during the elementary school years despite the shift from "learning to read" to "reading to learn."..

Twins and non-twin siblings: different estimates of shared environmental influence in early childhood

..Although many possibilities exist for explaining the special shared environment effect for twins, we suggest that cognitive-relevant experiences that are not shared by siblings are shared by twins because they are exactly the same age...

Genetic influences on the stability of attention-deficit/hyperactivity disorder symptoms from early to middle childhood

..A surprising finding emerging from multivariate quantitative genetic studies across diverse learning abilities is that most genetic influences are shared: they are "generalist", rather than "specialist"...

..Although each SNP accounts for a small amount of variance, their effects are additive and they can be combined in a 'SNP set' that can be used as a genetic risk index for MMI in behavioral genomic analyses...

..Thus, hyperactivity-impulsivity may serve to exacerbate inattentiveness over time. Findings are discussed in the context of developmental changes in ADHD symptoms...

The high heritability of educational achievement reflects many genetically influenced traits, not just intelligence

Eva KrapohlMedical Research Council Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King s College London, London SE5 8AF, United KingdomProc Natl Acad Sci U S A 111:15273-8. 2014

..Together with intelligence, these domains account for 75% of the heritability of GCSE. We conclude that the high heritability of educational achievement reflects many genetically influenced traits, not just intelligence. ..

..In contrast, though more varied, heterotypic continuity between some traits (i.e. the change from one type of anxiety-related behaviour into another over time) was mainly due to shared-environmental factors...

..Twin research has consistently shown substantial genetic influence on individual differences in cognitive ability; however, much less is known about the genetic and environmental aetiologies of school achievement...

Quantitative genetics in the era of molecular genetics: learning abilities and disabilities as an example

..41-0.60). Shared environmental influences were moderate (0.28, 0.19-0.37). We conclude that genetic variation contributes substantially to high g in Australia, the Netherlands, the United Kingdom and the United States...

Assessing reliability, heritability and general cognitive ability in a battery of cognitive tasks for laboratory mice

..We present a set of software tools for processing SNPMaP (SNP microarrays and pooling) data from CEL files to Relative Allele Scores in the rich R statistical computing environment...

Brain correlates of non-symbolic numerosity estimation in low and high mathematical ability children

Yulia KovasInstitute of Psychiatry, King s College London, London, United KingdomPLoS ONE 4:e4587. 2009

..This suggests that individual differences in mathematical ability are reflected in differential brain response during approximation...

Time to give up on a single explanation for autism

Francesca HappeFrancesca Happé, Angelica Ronald and Robert Plomin are at the Institute of Psychiatry, Kings College London, De Crispigny Park, London SE5 8AF, UKNat Neurosci 9:1218-20. 2006

..Twin data suggest largely nonoverlapping genes acting on each of these traits. At the cognitive level, too, attempts at a single explanation for the symptoms of autism have failed. Implications for research and treatment are discussed...

The future of genetics in psychology and psychiatry: microarrays, genome-wide association, and non-coding RNA

..To assess the genetic and environmental etiology of the co-occurence of ADHD symptoms and reading difficulties using the largest sample to date, distinguishing two dimensions of ADHD and two of reading...